microsoft surface pro

Hello people, I've been staring at specs and listings for days and I thought - what the hell ask someone else.. Do you think I should buy a Surface Pro 4 m3 4gb or for roughly the same price a secondhand Surface Pro 3 i5 - i7 packing 8gb? I know (in the loosest sense of the word) Surface 3...

Hello thank you for the brilliant forum. I have a question if anyone could answer it that would be great! Can I put the motherboard of a cosmetically damaged Surface Pro i7 into my Microsoft i3 and it behave it's self? Any in put would be gladly received. , All the best Steven